A long-term context is important for understanding past climatic variability. Although tree-ring widths (TRWs) are widely used as a proxy for reconstructing past climate, the use of annually-resolved ...values of δ13C and δ18O tree-ring stable isotopes (TRSIs) is increasing and may provide further valuable information. Here, we present a 487-year-long TRW chronology and 240-year-long TRSI chronology for Bosnian pine (Pinus heldreichii H. Christ) and compare them to each other. We demonstrate that both δ13C and δ18O values are better proxies for temperature, precipitation, and drought than TRW. The correlations between these climate parameters and TRSIs are strongest for the combined summer (JJA) period. The results of temporal and spatial field correlation indicate that TRSI chronologies are stable, reliable proxies for JJA precipitation reconstruction over the whole Balkan Peninsula and surrounding eastern Mediterranean region. However, the stability of the temperature signal of the both δ13C and δ18O chronologies declines after the 1950s. Our work supports the emerging evidence that TRSI data track climate variability more accurately than a conventional TRW approach and can be subsequently used for the reconstruction of past climate.
Gap regeneration in two old-growth forest reserves in Slovenia (Rajhenavski Rog) and Croatia (Čorkova Uvala) was analysed in relation to within gap light heterogeneity. Both reserves were located in ...the Dinaric mountain range in south-central Europe and were dominated by beech (Fagus sylvatica L.) – silver fir (Abies alba Mill.) forest communities with similar growing conditions. In total, the two largest gaps (700–2000 m2) in each reserve were included in the study (n = 4), plus a further four gaps in Rajhenavski Rog and three in Čorkova Uvala (200–500 m2). All the gaps were ∼10 years old and originated from one or two successive events, mostly due to a combination of fungi attack and windthrow. Consequently, all gaps had complex geometry and were covered by a well-developed regeneration layer. Each gap was mapped, followed by establishment of a N–S oriented 5 × 5 m grid within and around the area of the canopy opening. At the grid intersections 773, 1.5 × 1.5 m plots were established. On each plot, the coverage of tree regeneration and ground vegetation, seedling density in different height classes and browsing damage were recorded. In addition, the total stretched length and last growing season increment of the leading stem was measured on selected seedlings in each plot. Relative diffuse and direct radiation were estimated using digital hemispherical photographs. All plots were classified into four microsites according to direct and diffuse radiation levels, and microsites were tested for differences in regeneration height and density. While there was more woody regeneration and an almost fivefold higher (6.2 vs 1.3 m−2) average total regeneration density in Rajhenavski Rog, mainly due to a high (5.5 vs 0.6 m−2) density of beech, there was more ground vegetation and a higher density of silver fir seedlings in Čorkova Uvala. The within-gap regeneration patterns proved to be similar in both forest reserves and showed that 1-year-old seedlings of beech and silver fir and small beech seedlings preferably recruit on microsites under closed canopy or close to gap edges with lower levels of direct and diffuse radiation. There was no significant difference in density of large-beech seedlings among the microsites, yet height and height increment were higher on microsites receiving the highest levels of direct and diffuse radiation. Within-gap heterogeneity in light conditions appears to significantly influence general patterns of beech and silver fir regeneration, while the differences in total average density, regeneration and ground vegetation abundance and spatial distribution cannot solely be explained by light. Since climate, parent material, soil, exposition, relief and stand conditions were very similar between both reserves, it appears that these differences are a result of different densities of large herbivores, which are reported to be much higher in Rajhenavski Rog. This was also confirmed in our research, as much more browsing damage was found in Rajhenavski Rog compared with Čorkova Uvala. Implications for silvicultural practice are outlined.
Background and Purpose: The aim of this article is to create a virtual forest stand based on the field measurement of spatially separated sample plots and to examine its credibility based on the ...deviation of the basic characteristics of the virtual stand as compared to the field measurements.
Material and Methods: Field measurements were made on 20 circular sample plots with a 20 m radius, set on a 100x100 m grid. By using the univariate Ripley’s K function the regularity of the spatial pattern of trees was analysed. The diameter distribution and the frequencies of height within individual diameter class were mathematically fitted and used for generating the virtual stand. The whole process of generating the virtual stand was done in the R software. Area of study are even-aged silver fir stands in the Croatian Dinarides.
Results: The main unit of the virtual stand is a tree, with the purpose that the virtual stand can then be used as a basis for forest stand growth simulators. The result of the research was a virtual stand of 3 ha whose characteristics only slightly differed from the field measured plots. Within the virtual stand, special emphasis has been put on tree heights, which were generated according to the variability of tree height for trees of the same diameter at breast height.
Conclusions: Considering the distribution of diameters at breast height, tree heights, the number of trees, basal area and volume, the virtual stand has minimal deviations from the situation in the field and it adequately shows variability measured in the field.
Background and Purpose: Forest trees are adapted to the specific climatic conditions and other ecological factors that dominate within their distribution range. However, the climate is in constant ...flux. In addition to natural climatic oscillations, the climate has also been changed directly or indirectly by human activities. The issue of climate change is tied mostly to air temperature and precipitation. The objective of this study was to assess the potential influence of climate change on a part of the ecological niche of pedunculate oak (Quercus robur L.) in Croatia.
Materials and Methods: A forecast model was developed for the ecological niche of pedunculate oak in Croatia from the present day to 2080 using logistical regression, on the basis of a climate change model.
Results: Within the lowland areas of Croatia, the model forecasts an increase in the minimum temperatures of the coldest month and maximum temperature of the warmest month, and reduced precipitation in both the driest and wettest months.
Conclusion: The results indicate that climate change will negatively impact the ecological niche of pedunculate oak in the future.
•Multiple types of evidence yield an overview of the disturbance regime in Dinaric Mountain forests.•Variation in regime components from multiple agents results in a complex disturbance ...regime.•Intermediate severity disturbance events are characteristic of the regime.
Quantitative descriptions of natural disturbance regimes are lacking for temperate forest regions in Europe, primarily because a long history of intensive land-use has been the overriding driver of forest structure and composition across the region. The following contribution is the first attempt to comprehensively describe the natural disturbance regime of the dominant forest communities in the Dinaric Mountain range, with an emphasis on the range of natural variability of regime components for the main disturbance agents. Compared to other forest regions in Europe, the mountain range has a history of less intensive forest exploitation and provides a suitable record of natural disturbance processes. Our synthesis is based on multiple types of evidence, including meteorological information, historical documentation, evidence from old-growth remnants, and salvage logging data from National forest inventories. Taken together, the results show that no single disturbance agent dominates the regime in the dominant forest types (i.e. beech and mixed beech-fir forests), and any given agent exhibits remarkable variation in terms of severity and spatial extent both within and among individual disturbance events. Thunderstorm winds cause the most severe damage (i.e. near stand replacement), but blowdown patches are typically limited to stand-scales (e.g. 10s of ha). Ice storms and heavy snow typically cause intermediate severity damage and affect much larger areas (e.g. 100s of km2). A notable exception was the 2014 ice storm, which was nearly an order of magnitude larger and more severe than any other event recorded in the synthesis. Severe and prolonged periods of drought have occurred several times over the past century, and along with secondary insect damage (e.g. bark beetles), have caused episodes of forest decline. Overall, our synthesis indicates that on top of the background of relatively continuous gap dynamics, stand-scale intermediate severity events are an important part of the regime; these events likely have rotation periods that are less than the lifespan of a tree cohort (e.g. several centuries) and create canopy openings large enough to alter successional trajectories.
A number of practical examples of small scale natural regeneration of common beech were investigated in the period 2006–2010. In Croatia, the research area consisted of forest administrations of ...Zagreb, Koprivnica, Karlovac, Plitvice Lakes National Park and Žumberak – Samoborsko Gorje Nature Park, and outside Croatia it included Belgium, Czech Republic, Germany, Slovakia and Slovenia (Fig. 1). This paper presents the results of research into small scale regeneration of common beech in the form of groups (Fig. 2, Table 1), using the example of a Dinaric montane beech forest (as. Lamio orvalae-Fagetum /Ht. 1938/ Borhidi 1963) and small-stand regeneration, using the example of a beech forest with sedge (as. Carici pilosae-Fagetum Oberforfer 1957).Natural regeneration in virgin beech stands begins in the form of clusters and groups (Fig. 3 and 4, Table 2). This regeneration method can be applied in special purpose forests and in protection forests, since it forms structurally diverse stands that will satisfy non-market forest goods and services of these forests. It is also suitable for private forest owners because not only does it enable the concentration of treatments in small areas, but also allows the planning of a continuous yield.Small scale regeneration with shelterwood cuts in large complexes of managed forests is both possible and desirable. Regeneration over small areas at the level of small (1–3 ha) and medium (3–5 ha) stands has proven successful (Fig. 5, Table 3).Compared with classical regular management over large areas, small scale management is a closer-to-nature and more intensive management method. It requires the construction of a silvicultural plan that contains a map of initial regeneration gaps and directions of its expansion. Silvicultural treatments are applied simultaneously, but in different parts of the regeneration area. This type of management alleviates the application and supervision of silvicultural treatments and enables long-term and continuous planning of the felling cut.
Floodplain forests are the most rapidly disappearing ecosystem in the world, especially in temperate regions of Europe where anthropogenic influence has been pronounced throughout history. Research ...on primeval forests is crucial to further our understanding of their natural dynamics and interaction with climate but is limited by the lack of such preserved forests. The aim of this study was to investigate how a primeval floodplain forest in Southeastern Europe has responded to climate variability during the last 250 years through comparison of tree growth and climate, canopy disturbance and recruitment dynamic of two dominant tree species with different tolerances to flooding/drought. Our analysis revealed induced stress caused by several consecutive severe drought events in the 1940s, which led to a significant increase in sensitivity to increasing temperatures and decreasing river water levels. This trend is particularly pronounced in pedunculate oak. Age structure analysis revealed one larger episode of oak regeneration culminating after periods of intense growth release. Such period co-occurs with summer drought, which is part of a complex system of natural disturbances and a significant natural driver of the cyclical regeneration of primeval oak ecosystems.
Where are Europe's last primary forests? Sabatini, Francesco Maria; Burrascano, Sabina; Keeton, William S. ...
Diversity & distributions,
October 2018, Volume:
24, Issue:
9/10
Journal Article
Peer reviewed
Open access
Aim: Primary forests have high conservation value but are rare in Europe due to historic land use. Yet many primary forest patches remain unmapped, and it is unclear to what extent they are ...effectively protected. Our aim was to (1) compile the most comprehensive European-scale map of currently known primary forests, (2) analyse the spatial determinants characterizing their location and (3) locate areas where so far unmapped primary forests likely occur. Location: Europe. Methods: We aggregated data from a literature review, online questionnaires and 32 datasets of primary forests. We used boosted regression trees to explore which biophysical, socio-economic and forest-related variables explain the current distribution of primary forests. Finally, we predicted and mapped the relative likelihood of primary forest occurrence at a 1-km resolution across Europe. Results: Data on primary forests were frequently incomplete or inconsistent among countries. Known primary forests covered 1.4 Mha in 32 countries (0.7% of Europe's forest area). Most of these forests were protected (89%), but only 46% of them strictly. Primary forests mostly occurred in mountain and boreal areas and were unevenly distributed across countries, biogeographical regions and forest types. Unmapped primary forests likely occur in the least accessible and populated areas, where forests cover a greater share of land, but wood demand historically has been low. Main conclusions: Despite their outstanding conservation value, primary forests are rare and their current distribution is the result of centuries of land use and forest management. The conservation outlook for primary forests is uncertain as many are not strictly protected and most are small and fragmented, making them prone to extinction debt and human disturbance. Predicting where unmapped primary forests likely occur could guide conservation efforts, especially in Eastern Europe where large areas of primary forest still exist but are being lost at an alarming pace.
Sažetak
Brojna istraživanja pokazuju da su šume obične jele ugrožene klimatskim promjenama, posebice na južnim rubovima njihova rasprostranjenja gdje su negativni učinci zatopljenja izraženiji. Šume ...jele i crnoga graba rastu od 850 m do 1150 m nadmorske visine na kontinentalnoj padini planine Biokovo na karakterističnom vrtačastom reljefu, koji utječe na mozaični raspored golih stijena, tla, vegetacije i šumske prostirke. Cilj ovoga istraživanja je, po prvi puta, za termofilne i najjužnije šume jele i crnoga graba u Hrvatskoj utvrditi fiziografske značajke šumske prostirke i tla te sadržaj teških metala u površinskom sloju tla, pa usporediti dobivene podatke za šumsku prostirku i tlo s podacima za ostale jelove zajednice Hrvatske. Terenskim opažanjima u nizu vrtača utvrđeno je da ljeti (sušno i toplo razdoblje) iz jamskih otvora i pukotina struji hladan zrak, stvarajući u vrtačama specifične mikroklimatske uvjete koji pogoduju jeli i mogu potencijalno biti važan čimbenik njenog opstanka. U šumi jele i crnoga graba utvrđene su značajne količine šumske prostirke i zalihe ugljika, koje su u rasponu od 2,86 kg m–2 do 11,59 kg m–2, odnosno od 1,13 kg m–2 do 4,89 kg m–2 uz izrazitu prostornu varijabilnost. Po fiziografskim značajkama površinskog sloja tla šume jele i crnoga graba grupiraju se uz bukovo-jelove šume sjevernog Velebita i Gorskog kotara, što upućuje na dominantan pedogenetski utjecaj (karbonatnog) matičnog supstrata. Osnovni limitirajući čimbenik tla šuma jele i crnoga graba njegova je mala dubina. U površinskom sloju tla utvrđen je povišen do vrlo visok sadržaj teških metala Cu, Pb, Zn, Ni i Cd.
Summary
Climate change is affecting the availability of resources and conditions critical to the life and survival of forest communities and the species that inhabit them, especially at the edges of their distribution. Numerous studies indicate that fir forests are threatened by climate change, especially at the southern edges of their range where the negative effects of warming are more pronounced.
The aim of this study was to determine for the first time for the thermophilic and southernmost fir and hornbeam forests (
Ostryo-Abietetum
) in Croatia the physiographic characteristics of the forest floor and soil, as well as the content of heavy metals in topsoil layer, and to compare the obtained data for the forest floor and soil with data for other fir communities in Croatia. These forests grow from 850 m to 1150 m a.s.l. on the continental slope of Biokovo Mountain on a characteristic sinkhole relief which influences the mosaic arrangement of soil, vegetation and forest floor.
Field observations in a number of sinkholes have shown that in summer (the dry and hot period) cold air flows in from caves and cracks and creates specific microclimatic conditions in the sinkholes that are favourable for fir and could be a key factor for its survival.
At the bottom of the sinkholes, fir trees dominate, rockiness is less pronounced and Mollic Leptosol and Leptic Cambisol alternate. The forest floor mass (load) is higher. On the other hand, at the edges of the sinkholes, the rockiness is more pronounced, the soil is either very shallow (Mollic Leptosol) or absent, and the forest floor mass is lower. Thermophilic tree species dominate, while firs are sporadic or absent.
Considerable amounts of forest floor and carbon stocks were determined in the fir and hornbeam forests, ranging from 2.86 kg m-2 to 11.59 kg m-2 and 1.13 kg m-2 to 4.89 kg m-2, respectively, with high spatial variability. According to the physiographic characteristics of the surface layer of the soil, fir and hornbeam forests are grouped together with the beech-fir forests of the northern Velebit and Gorski kotar, indicating the dominant pedogenetic influence of the (carbonate) parent substrate. The basic limiting factor of the soil of fir and hornbeam forests is its shallow depth. Elevated to very high content of the heavy metals Cu, Pb, Zn, Ni and Cd were found in the topsoil.
•Growth limited by high summer temperatures and water availability in the Dinaric MTS.•Earlywood blue intensity contains a stronger recent drought signal than ring width.•Spruce TRW response is ...stronger than in fir, but similar in EWBI of both species.•Recent spruce growth decline linked to increasing summer temperature and drought.•Ongoing climate change may have a strong impact on vitality and forest development.
The past century has witnessed a global trend of increasing green house gas emissions, causing a rise in temperatures, changing hydroclimatic patterns and increasing occurrence of climatic extremes. Despite their importance for environmental conservation, scientific research and forest management, primary montane forests of the Dinaric Mts remain insufficiently studied. In this study, we examined the relationship between climate and growth of Norway spruce (Picea abies (L.) H. Karst.) and silver fir (Abies alba Mill.) in the primary forests of Smrčeve doline, located in Northern Velebit National Park, Croatia. Using dendrochronological methods, the temporal relationships between tree ring width (TRW) and blue intensity (BI) were assessed over the 1901–2014 interval, in relation to instrumental climatic data, including temperature, precipitation and self‐calibrating Palmer Drought Severity Index (scPDSI). TRW and earlywood BI (EWBI) chronologies of both species exhibited a clear negative response to summer temperatures, while also showing a positive relationship with summer precipitation and moisture, implying that tree growth in the region is water-limited. Generally, correlation values of EWBI were stronger compared to the TRW chronologies. Although both species showed a degree of common growth response to climatic extremes, the strength of correlations with the most responsive climatic variables was temporally unstable and showed considerable variability in both tree ring parameters. The observed differential response of the two species to climate indicates that the anticipated increase in dry conditions due to climate change could potentially alter the future development and composition of these primary forests by shifting competitive pressures in favor of silver fir. Increasing drought stress around the Mediterranean could have major negative implications for these water-limited primary forests.
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